Graduate
  1. Physical Chemistry  1.1. Thermodynamics  1.1.1. Laws of Thermodynamics  1.1.2. Enthalpy and heat capacity  1.1.3. Entropy and free energy  1.1.4. Phase Equilibrium  1.1.5. Statistical thermodynamics  1.1.6. Thermodynamic cycle  1.1.7. Fugacity and activity  1.2. Quantum Chemistry  1.2.1. Principles of quantum mechanics  1.2.2. Schrödinger Equation  1.2.3. Particle in a box  1.2.4. Operators and eigenvalues  1.2.5. Atomic orbitals  1.2.6. Molecular orbital theory  1.2.7. Perturbation theory  1.2.8. Valence bond theory  1.2.9. Hybridization and chemical bonding  1.3. Chemical kinetics  1.3.1. Rate laws and reaction mechanisms  1.3.2. Collision theory  1.3.3. Transition state theory  1.3.4. Enzyme Kinetics  1.3.5. Chain Reactions and Polymerization  1.3.6. Photochemical reactions  1.4. Statistical mechanics  1.4.1. Partitioning functions  1.4.2. Molecular distribution functions  1.4.3. Boltzmann Distribution  1.4.4. Bose–Einstein and Fermi–Dirac statistics  1.5. Spectroscopy  1.5.1. Rotational Spectroscopy  1.5.2. Vibrational Spectroscopy  1.5.3. Electronic Spectroscopy  1.5.4. Nuclear magnetic resonance spectroscopy  1.5.5. Mass Spectrometry  1.5.6. Raman Spectroscopy  1.5.7. Electron paramagnetic resonance spectroscopy  1.6. Surface and colloidal chemistry  1.6.1. Absorption isotherm  1.6.2. Surface tension and wetting  1.6.3. Colloidal Stability  1.6.4. Catalysis  1.6.5. Emulsions and micelles  1.7. Electrochemistry  1.7.1. Nernst equation  1.7.2. Electrochemical cells  1.7.3. Conductivity and mobility  1.7.4. War  1.7.5. Fuel cells  1.7.6. Electrolysis
  2. Organic chemistry  2.1. Reaction mechanism  2.1.1. Nucleophilic substitution reactions  2.1.2. Electrophilic addition reactions  2.1.3. Elimination reactions  2.1.4. Rearrangement reactions  2.1.5. Radical reactions  2.1.6. Pericyclic reactions  2.2. Spectroscopy and structural determination  2.2.1. UV-Vis Spectroscopy  2.2.2. IR Spectroscopy  2.2.3. NMR Spectroscopy  2.2.4. Mass Spectrometry  2.2.5. X-ray crystallography  2.3. Stereoscopic  2.3.1. Chirality and optical activity  2.3.2. Structural analysis  2.3.3. Geometrical isomerism  2.3.4. Dynamic Stereochemistry  2.4. Organometallic Chemistry  2.4.1. Organolithium and organomagnesium reagents  2.4.2. Palladium-catalyzed cross-coupling reactions  2.4.3. Transition Metal Complexes  2.4.4. Metal–carbon bond  2.5. Polymer chemistry  2.5.1. Polymerization mechanism  2.5.2. Polymer Characteristics  2.5.3. Biodegradable Polymer  2.5.4. Conducting polymer  2.5.5. Supramolecular polymers  2.6. Medicinal chemistry  2.6.1. Drug design and development  2.6.2. Pharmacokinetics and pharmacodynamics  2.6.3. Structure-activity relationships  2.6.4. Molecular docking and drug screening
  3. Inorganic chemistry  3.1. Coordination chemistry  3.1.1. Crystal field theory  3.1.2. Ligand field theory  3.1.3. Spectrochemical Series  3.1.4. Chelation and stability  3.2. Organometallic Chemistry  3.2.1. Metal Carbonyls  3.2.2. Catalysis by organometallic complexes  3.2.3. Metallocenes  3.3. Bio-inorganic chemistry  3.3.1. Metalloproteins and enzymes  3.3.2. The role of metals in biological systems  3.3.3. Metal ion transport and storage  3.4. Solid state chemistry  3.4.1. Crystal Structures  3.4.2. Band theory of solids  3.4.3. Superconductors  3.4.4. Defects in the crystal  3.5. Lanthanides and Actinides  3.5.1. Electronic configuration in lanthanides and actinides  3.5.2. Coordination chemistry of the lanthanides  3.5.3. Magnetic Properties of Lanthanides
  4. Analytical chemistry  4.1. Chromatography  4.1.1. Gas Chromatography  4.1.2. High Performance Liquid Chromatography  4.1.3. Thin Layer Chromatography  4.2. Spectroscopic Techniques  4.2.1. Atomic absorption spectroscopy  4.2.2. X-ray diffraction  4.2.3. Inductively coupled plasma spectroscopy  4.3. Electroanalytical methods  4.3.1. Potentiometry  4.3.2. Voltammetry  4.3.3. Colometry  4.4. Mass Spectrometry  4.4.1. Ionization Technique  4.4.2. Fragmentation Pattern  4.5. Chemometrics  4.5.1. Multidisciplinary analysis  4.5.2. Machine Learning in Chemistry
  5. Theoretical and Computational Chemistry  5.1. Molecular dynamics simulation  5.1.1. Force fields and energy minimization  5.1.2. Monte Carlo simulation in molecular dynamics simulations  5.2. Quantum chemical methods  5.2.1. Hartree–Fock theory  5.2.2. Density functional theory  5.2.3. Semi-empirical methods  5.3. Computational drug design  5.3.1. Molecular Docking  5.3.2. QSAR Modeling  5.3.3. Virtual Screening
  6. Biochemistry  6.1. Enzyme Kinetics  6.1.1. Michaelis-Menten kinetics  6.1.2. Inhibition mechanism  6.2. Metabolism and Bioenergetics  6.2.1. Glycolysis  6.2.2. Citric acid cycle  6.2.3. Electron transport chain  6.3. molecular Biology  6.3.1. DNA replication and repair  6.3.2. Protein synthesis  6.3.3. Gene Regulation  6.4. Structural Biochemistry  6.4.1. Protein Folding  6.4.2. Membrane Biophysics
  7. Environmental Chemistry  7.1. Atmospheric Chemistry  7.1.1. Greenhouse gases  7.1.2. Ozone depletion  7.1.3. Air pollutants and smoke  7.2. Water Chemistry  7.2.1. pH and water hardness  7.2.2. Wastewater treatment  7.2.3. Aquatic Chemistry  7.3. Soil Chemistry  7.3.1. Heavy metal contamination  7.3.2. Soil pH and Buffering  7.3.3. Nutrient cycling  7.4. Toxicology and Chemical Safety  7.4.1. Toxicokinetics  7.4.2. Risk Assessment in Toxicology and Chemical Safety in Environmental Chemistry  7.4.3. Effects of pollutants on the environment

Graduate → Physical Chemistry ↓


Surface and colloidal chemistry


Surface and colloidal chemistry is a fascinating branch of physical chemistry that deals with the study of surfaces, interfaces, and colloidal systems. This field is important in understanding the phenomena occurring at the microscopic and macroscopic levels, which impact a variety of scientific and industrial processes.

Surface chemistry

In surface chemistry, we focus on the boundary between two phases, such as solid-liquid, liquid-gas, solid-gas, etc. The surface of a substance is where it interacts with its environment, causing various physical and chemical changes. A key aspect of this field is adsorption, a process in which molecules stick to a surface.

To understand the process of adsorption, consider an activated charcoal filter used in water purification. Charcoal has a large surface area, allowing it to effectively adsorb impurities from water.

In the above figure, the grey rectangle represents a solid surface, while the circles represent various molecules absorbed on it.

Types of absorption

There are two primary types of adsorption:

  • Physical absorption: It is a physical absorption process in which the forces involved are weak van der Waals forces. It is usually reversible. For example, gases such as nitrogen and oxygen can be physically absorbed on activated carbon.
  • Chemical absorption: This involves chemical bonds between the adsorbate and the surface, making it strong and often irreversible. An example of this is the adsorption of hydrogen on the surface of nickel, where the hydrogen molecules dissociate and form bonds with the nickel atoms.

Colloidal chemistry

Colloidal chemistry deals with the study of systems where one substance is dispersed in another, resulting in stable systems with particle sizes typically ranging from 1 nm to 1 micron. These particles do not readily settle and remain distributed throughout the medium, forming a "colloid". Common examples include milk, paint, and fog.

Examples of colloids

There are many types of colloidal systems depending on the dispersion medium and dispersed phase.

Dispersed phase Dispersion medium Example
Solid Liquid Paint
Liquid Liquid Milk
Gas Liquid Foam (e.g., whipped cream)

Formation of colloids

Colloids can be formed in two primary ways:

  • Dispersion: Breaking up large particles into smaller particles that can remain suspended. For example, grinding solid particles to form colloids.
  • Condensation: Small particles come together to form larger particles, but they are not heavy enough to settle. This occurs in cloud formation, where water molecules condense to form clouds.

Importance of colloids

Colloids play an important role in many industries:

  1. Food industry: Emulsions such as mayonnaise are colloids. The consistency and stability of foods often depend on colloidal properties.
  2. Pharmaceuticals: Drugs can be delivered more effectively in colloidal form.
  3. Environmental science: Colloids are essential in water purification processes, where pollutants are removed through adsorption on colloidal particles.

Stability of colloids

The stability of colloidal systems is an important aspect, and it can be affected by several factors:

  • Electrical charge: Colloidal particles have electrical charge, which helps them repel each other and stay dispersed.
  • Protective layer: In some colloids, small molecules can form a protective layer around the colloidal particles, preventing them from aggregating.
  • Viscosity of the medium: High viscosity may help keep the particles suspended.

A classic demonstration of stabilization due to charge is the phenomenon known as Brownian motion, which involves the random motion of particles within a fluid, which contributes to colloidal stability.

In the figure, the blue dots represent particles undergoing Brownian motion, which helps keep them homogeneously distributed.

Surface and interfacial tension

Surface tension is another important factor in surface chemistry. It is the energy required to increase the surface area of a liquid due to intermolecular forces. For water, these forces are relatively strong, causing water to form droplets when placed on a flat surface.

The figure above shows a drop of water on a flat surface, illustrating the concept of surface tension. The curved line represents the surface of the drop. The forces acting along this curvature produce surface tension.

Interfacial tension

Interfacial tension is similar to surface tension, but occurs at the interface between two immiscible liquids. For example, oil and water exhibit interfacial tension, which affects the ability of the liquids to mix.

Surfactants are substances that reduce surface and interfacial tension. They have a hydrophobic tail and a hydrophilic head, which allows them to position themselves at the interface between oil and water, reducing the tension and promoting mixing.

R-(CH2)n-SO4^(-)

In the above formula, R is the hydrophilic head and (CH2)n represents the hydrophobic tail, indicating a typical surfactant structure.

Applications of surface and colloidal chemistry

There are many applications of the principles of surface and colloidal chemistry including:

  • Detergents and soaps: These are surfactants that clean surfaces and fabrics by emulsifying fats and oils, and aiding in their removal.
  • Cosmetics: Emulsions are fundamental in making lotions and creams by dispersing oil in water or vice versa.
  • Industrial processes: Flotation is a separation technique that uses differences in surface properties to separate minerals and ores.
  • Nanomedicine: Colloids are used in the development of therapeutic nanoparticles for drug delivery.

Conclusion

Understanding surface and colloidal chemistry is essential for diverse scientific and practical applications. The principles governed by molecular interactions on surfaces and in colloids allow innovative approaches to solve environmental, industrial, and biomedical challenges. As technology advances, the understanding and manipulation of surface and colloidal systems continues to grow, providing profound insights and applications in a variety of fields.


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Surface and colloidal chemistry

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